I have a 05 evo with TBE, intake and lower intercooler pipe. I dont race the car, but I do drive it almost daily. The car has been flashed for 93 octane, but where i live it's hard to find 93, although it is avaliable. 80% of the gas i get is 93 but on some rare occasions I have to get 91. (Where I live 91 and 93 are both considered premium). What I am asking is if using 91 will hurt anything if used only when necessary. Should i have the car reflashed to 91 octane, if so is it ok to then use 93 sometimes, or do i need to always use the ocatane level the car was flashed for.

I thought ECU flashed cars only take affect at WOT?

Bump

It's not a good idea, but if you drive very carefully and stay out of boost, you'll probably be ok. Just don't cause timing to advance more than a little bit and the lower octane will have no effect.

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You can leave it the way it is flashed for and try to put 93 in as much as possible. I would keep a bottle or two of octane booster in your car, and use it when you have to put in 91. Then you should be alright.

the ecu will still pull timing if it knocks, it's not set in stone, but ask in the forum of your flasher

i would agree i would stay away from the lesser octaine but ya i think you otta be fine just stay out of the boost..

knock knock... who's there ... knock knock ... damn-it who's there..... KNOCK KNOCK...

You car will knock bad under boost. Disconnect the boost solenoid and run on the waste gate spring (12psi).

true that

yeah, try to drive very lightly and stay away from boost and high revs. For most "stop and go" driving, you're probably okay.

I would not trust octane booster in any way. Start using 93 again, get your car flashed again for 91, or call your tuner.

Stay off of the boost and you'll be fine. But good luck staying off the boost.

i cant believe no one knows crap about it the cart will be fine it will pull timing if it senses knock dont worry about it put 91 in it and drive the car nothing will happen

No, it won't be fine. Just because the ECU sees knock and pulls timing doesn't mean there won't be a damaging amount of detonation. Remember, the ECU pulls timing AFTER it detects enough knock. Either never use 91 or get tuned for 91 and then use 93 when available...